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The extraction of pertechnetate (TcO4−) and perrhenate (ReO4−) by tributyl phosphate (TBP) has been extensively studied, but the structure of the extracted species is subject to debate. In this work, the extraction behavior of TcO4− and ReO4− from both HNO3 and HCl media by TBP in n-dodecane was studied by examining the effects of acid concentration, extractant concentration, and temperature on the extraction. The two anions displayed similar extraction behavior in both the HNO3 and HCl systems, where the distribution ratio of TcO4− was slightly higher than that of ReO4−. The measurement of water content in the organic phase and dynamic light scattering were carried out, which in combination with the extraction behavior indicated that ReO4− was extracted as [H+ReO4−(H2O)8·(TBP)4] and formed microemulsions in the organic phase. Theoretical calculations were performed on the structure of both [H+ReO4−(H2O)8·(TBP)4] and [H+TcO4−(H2O)8·(TBP)4]. The TBP molecules interacted with the [H+ReO4−(H2O)8] and [H+TcO4−(H2O)8] clusters through hydrogen bonding between H2O and the O=P groups, i.e., ReO4− and TcO4− underwent outer-sphere coordination with TBP in the organic phase. Results in this work provide valuable insights into the structures of ReO4− and TcO4− extracted into the organic phase by TBP, and also assist in the analysis of TcO4− species in the PUREX process. [ABSTRACT FROM AUTHOR]

99Tc is a long-lived radionuclide present in large amounts as TcO4- anion in used nuclear fuel. Its removal from the waste stream is highly desirable because of its interference capability with actinide separation and its volatile nature during the nuclear waste vitrification process. Despite the progress achieved in the past few years, the design of anion-exchange materials with optimized Tc uptake property and improved stability under the extreme condition, is still a research goal beneficial for reducing the volume of secondary radioactive solid waste generated during the waste partitioning process. However, their design philosophy remains elusive, with challenges coming from charge repulsion, steric hindrance, and insufficient reactive sites within the materials. Herein, we present a design philosophy of cationic polymer network materials for TcO4- separation by systematic precursor screening and structure prediction. This affords an optimized material, SCU-CPN-2 (SCU=Soochow University), with extremely high positive charge density while maintaining high radiation resistance. SCU-CPN-2 exhibits a record high adsorption capacity (1,467 mg/g towards the surrogate ReO4-) compared to all anion-exchange materials reported up to date. In addition to ultrafast adsorption kinetics, SCU-CPN-2 has remarkable selectivity over nitrate and sulfate, and facile recyclability. [ABSTRACT FROM AUTHOR]

Heat capacity for 1-hexyl-3-methyl imidazolium perrhenate ionic liquid [C6MIM][ReO4] in the temperature range from 79 to 396 K has been measured by a fully automated adiabatic calorimeter. For [C6MIM][ReO4], glass transition temperature, the melting temperature, standard molar heat capacity, enthalpy and entropy of solid–liquid phase transition were determined to be (202.164 ± 0.405) K, (226.198 ± 0.265) K, (480.702 ± 0.013) J K−1 mol−1, (15.665 ± 0.195) kJ mol−1 and (69.250 ± 0.780) J K−1 mol−1, respectively. In addition, the thermodynamic characteristics and solid–liquid phase change behavior of [C6MIM][ReO4] were compared with the ones of [C7MIM][ReO4] reported in the literature. The thermodynamic functions (HT− H298.15), (ST− S298.15) and (GT− G298.15), for the compound in the experimental temperature range were calculated. [ABSTRACT FROM AUTHOR]

The ionic liquid 1-(2-methoxyethyl)-3-ethyl imidazolium perrhenate [C22O1IM][ReO4] was prepared in the laboratory firstly, and its structure was confirmed by 1H NMR and 13C NMR. The heat capacities were precisely measured in the temperature range from 78 to 392 K by means of a fully automated adiabatic calorimeter. For [C22O1IM][ReO4], the melting temperature, standard molar heat capacity, molar enthalpy, and molar entropy of solid–liquid phase transition were determined to be (211.826 ± 0.130) K, (142.31 ± 0.34) J K−1 mol−1, (14.382 ± 0.046) kJ mol−1, and (67.93 ± 0.22) J K−1 mol−1, respectively. And the experimental values of molar heat capacities were fitted to a polynomial equation using least square method in the appropriate temperature ranges. The thermodynamic functions (HT − H298.15) and (ST − S298.15) were also obtained from the heat capacity data in the experimental temperature range with an interval of 5 K. [ABSTRACT FROM AUTHOR]

The effect of Bacillus spp. on Re(VII) and Se(IV) diffusion in compacted GMZ bentonite was investigated by a through-diffusion method. Bacillus spp. had no significance effect on the effective diffusion coefficient (De) and the accessible porosity (εacc) of Re(VII), whereas a decrease of De and an increase of distribution coefficient (Kd) were observed for Se(IV). Moreover, Archie's law and an exponential decay equation were employed to fit the De value of Re(VII) and Se(IV). [ABSTRACT FROM AUTHOR]

Low-temperature heat capacities of the 1-heptyl-3-methyl imidazolium perrhenate ionic liquids have been measured by a high-precision automated adiabatic calorimeter over the temperature range from 78 to 400 K. In this report, the standard molar heat capacity was determined to be 679.438 J K−1 mol−1. The melting temperature at 207.873 ± 0.374 K has been discovered by the heat-capacity curve. The experimental values of molar heat capacities were fitted to two polynomial equations of heat capacities (Cp,m) by least square method. Meanwhile, the thermodynamic functions (HT − H298.15), (ST − S298.15), and (GT − G298.15) were also calculated in the temperature range from 298.15 to 400 K with the interval of 5 K. [ABSTRACT FROM AUTHOR]

The monoclinic modification of [Cu(NH)](ReO) complex salt in the range 100-410 K is studied by single crystal X-ray diffraction. The crystallographic data for 300 K are as follows: a = 10.6123(3) Å, b = 7.5443(2) Å, c = 15.2261(4) Å, β = 108.406(1)°, V = 1156.67(5) Å, space group Р2/ n, Z = 4, d = 3.623 g/cm. The coordination environment of the Cu atom, being a distorted square formed by four nitrogen atoms with Cu-N of 1.997-2.018 Å, is completed by the contacts with two oxygen atoms Cu...O of 2.472 Å and 2.598 Å. The comparative crystal chemical analysis with the triclinic modification of [Cu(NH)](ReO) known in the literature is performed. [ABSTRACT FROM AUTHOR]

The X-ray in-situ study of [Cu(NH)](ReO) complex salt is carried out on heating up to 500 K. The product obtained at this temperature is a new crystalline phase [Cu(NH)(μ-ReO)] with the following unit cell parameters: a = 14.7523(3) Å, b = 5.8559(1) Å, c = 5.6290(1) Å, β = 111.387(1)°, V = = 452.799(2) Å, space group C2/ m, Z = 2, d = 4.386 g/cm. The coordination polyhedron of the Cu atom is a distorted octahedron formed by two nitrogen atoms (Cu-N 2.195 Å), and four oxygen atoms (Cu-О 2.306 Å). The structure consists of infinite [Cu(NH)(μ-ReO)] chains, the shortest N(H)...O distances between the chains being 2.82 Å. [ABSTRACT FROM AUTHOR]

Humic acid is ubiquitous in soils and water. It affects the migration of radionuclides by complexation or redox reactions. The effect of humic acid on the diffusion of ReO in GMZ bentonite was investigated at dry density from 1,300 to 1,800 kg/m. The effective diffusion coefficient D and rock capacity factor α were measured by through-diffusion method. The D decreased from 5.5 to 0.59 × 10 m/s and α decreased from 0.2 to 0.12 with the dry density increasing from 1,300 to 1,800 kg/m. The retardation factor R in GMZ bentonite at three dry densities was obtained, which were less than one. Archie's law was used to describe the relationship between accessible porosity ε and D. An empirical parameter n ( n = 2.2 ± 0.2) was obtained for Re diffusion in GMZ bentonite in the presence of humic acid. [ABSTRACT FROM AUTHOR]

Perrhenate (ReO) was used as nonradioactive surrogate for the radionuclide pertechnetate (TcO) to investigate the potential of using starch-stabilized zero valent iron (ZVI) nanoparticles for reductive immobilization of pertechnetate in soil and groundwater. Batch kinetic tests indicated that the starch-stabilized ZVI nanoparticles were able to reductively remove ∼96% of perrhenate (10 mg/L) from water within 8 h. XRD analyses confirmed that ReO was the reduction product. A pseudo-first-order kinetic model was able to interpret the kinetic data, which gave a pseudo first order rate constant ( k) value of 0.43 h at pH 6.9 and room temperature (25°C). Increasing solution pH up to 8 progressively increased the reaction rate. However, highly alkaline pH (10) resulted in much inhibited reaction rate. Consequently, the optimal pH range was identified to be from 7 to 8. Increasing solution temperature from 15 to 45°C increased k from 0.38 to 0.53 h. The classical Arrhenius equation was able to interpret the temperature effect, which gave a low activation energy value of 7.61 kJ/mol. When the ReO-loaded loess was treated with the stabilized nanoparticles suspension ([Fe]=560 mg/L), the water leachable ReO was reduced by 57% and nearly all eluted Re was in the form of ReO. This finding indicates that starch-stabilized ZVI nanoparticles are promising for facilitating in situ immobilization of ReO in soil and groundwater. [ABSTRACT FROM AUTHOR]

Radiolabeled biomolecules are routinely used for clinical diagnostics. Tc is the most commonly used radioactive tracer in radiopharmaceuticals. Re and Re are also commonly used as radioactive tracers in medicine. However, currently available methods for radiolabeling are lengthy and involve several steps in bioconjugation processes. In this work we present a strategy to engineer proteins that may selectively recognize the perrhenate (ReO) ion as a new way to label proteins. We found that a molybdate (MoO)-binding protein (ModA) from Escherichia coli can bind perrhenate with high affinity. Using fluorescence and isothermal titration calorimetry measurements, we determined the dissociation constant of ModA for ReO to be 541 nM and we solved a crystal structure of ModA with a bound ReO. On the basis of the structure we created a mutant protein containing a disulfide linkage, which exhibited increased affinity for perrhenate ( K = 104 nM). High-resolution crystal structures of ModA (1.7 Å) and A11C/R153C mutant (2.0 Å) were solved with bound perrhenate. Both structures show that a perrhenate ion occupies the molybdate binding site using the same amino acid residues that are involved in molybdate binding. The overall structure of the perrhenate-bound ModA is unchanged compared with that of the molybdate-bound form. In the mutant protein, the bound perrhenate is further stabilized by the engineered disulfide bond. [ABSTRACT FROM AUTHOR]

The synthesis and anion binding properties of a neutral macrocyclic receptor bearing H-bond donor coordination sites are described. The anion binding studies by use of UV-vis and 99Tc NMR methods revealed that the receptor can coordinate perrhenate and pertechnetate in dimethylsulfoxide and chloroform solutions with the relatively high binding constants, viz. log Ka > 4. The coordination mode of the perrhenate to the receptor was determined by a single-crystal X-ray diffraction analysis. [ABSTRACT FROM AUTHOR]

The results of investigation of the regularity of 188Re binding with KNaHEDP and hydrolysis of the complex compound (188Re-KNaHEDP) have shown that its quality depends to a considerable extent on the reaction conditions. Concentrations of a reducing agent (Sn2+) and stable rhenium in the 188Re eluate, as the carrier, influence essentially the rate of formation and stability of 188Re complex with KNaHEDP. The results of the kinetic investigations of the 188Re-KNaHEDP complex formation prove that the reaction character bears a direct relationship to the concentrations of the complexing agent (Re) and the reducer (Sn2+). The higher ratio of Re7+: Sn2+ concentrations, the more effectively 188Re binds with KNaHEDP. The obtained results prove that for 188Re binding with KNaHEDP with the efficiency not less than 95 % the optimum concentration of stable rhenium in the reaction mixture is 0.54×10−6 mol·ml−1 (0.1 mgMl−1) and the ratio of Re7+: Sn2+ concentrations should not be lower than 10: 1. [ABSTRACT FROM AUTHOR]